Light-emitting diode (LED) lighting typically uses nitridosilicates and oxonitridosilicates materials to enhance color rendering index (CRI) and chemical stability. In particular, nitridosilicates have high condensed frameworks, and thus, have stable chemical structures and exhibit thermal stability. Following crystal field splitting theory and nephelauxetic effects, nitride phosphors can emit more red light than oxide phosphors. For example, a blue-emitting diode can be used to excite a nitride phosphor to provide red light. U.S. Pat. No. 6,649,946 discloses nitride phosphors that expose yellow to red emitting phosphor, such as (Ca, Sr, Ba)xSiyNz:Eu (z=2/3x+4/3y) (for example, (Ca, Sr, Ba)2-xSi5N8:Eux). These types of phosphors are synthesized at normal pressure. It has been observed that since nitride phosphors corresponding excitation spectrum does not match the emission spectrum of a blue light-emitting LED, such as an indium gallium nitride (InGaN) LED, existing nitride phosphors less efficient as red light-emitting phosphors than desirable. Accordingly, the corresponding LED devices have less flexibility and capability to tune the colors and the CRI.
Therefore, a LED device integrated with a phosphor material having a proper excitation spectrum and a method of making the same are needed.